Diminishing Ethylbenzene in Methylation of Benzene with Methanol: Disentanglement of Methanol to Olefin Reactions over MFI Gallium Silicate

Abstract

Methylation of benzene with methanol provides an efficient route to utilize the surplus benzene in aromatic united plants, facing a primary challenge from the ethylbenzene (EB) as the side product. This work discovers that EB selectivity can be significantly limited utilizing nanosized MFI type gallium silicate. Experiment and simulation results reveal diminished EB owing to the acid strength and diffusion capability. Gallium silicate zeolite, with much weaker acidity than aluminum silicate zeolite, favored higher energy barriers for polymethylbenzene formation, important precursors in methanol to olefin reactions, effectively suppressing ethene and EB. Additionally, the smaller particle size led to improved diffusion, facilitating the effusion of heavy aromatics. Therefore, nanosized MFI type gallium silicate could achieve an EB selectivity lower than 0.1% with toluene and xylene selectivities exceeding 90%. Our study provided a feasible strategy for adjusting the coordination–competition relationship between the main and side reaction mechanisms based on the synergistic effect of active sites and mass transfer.